1. Field
The present disclosure relates to electronic integrated circuits (“ICs”), and more specifically to RF power amplifier (“PA”) integrated circuits.
2. Related Art
Most radio transceivers, such as the cell phones that are a ubiquitous feature of modern life, require an RF PA circuit to boost the transmit signal to a level sufficient to be received by a target transceiver, such as a cellular base station. In this highly competitive field, consumers value increases in transceiver features such as battery life, operational range and signal quality. The RF power amplifier strongly impacts each of these features. Designs that increase signal quality and transmit power will generally increase operational range, but will thereby negatively affect battery life and/or cost unless the PA power efficiency is also increased.
Increases in PA power efficiency will generally enable improvements in battery life for a given signal quality and operational range. Also, because removing waste heat incurs costs, enhancements to efficiency will generally also reduce the costs incurred to remove waste heat. Power efficiency is thus one aspect of the overall cost efficiency of an RF PA designed for a selected performance level. Other aspects of cost efficiency, such as integrated circuit size and other manufacturing considerations, should be concurrently addressed in order to produce an RF PA that provides the best overall value to a user.
Mobile transceivers, such as mobile telephones, must operate at widely varying distances from a base station or other target transceiver, and under widely varying signal path conditions. Accordingly, all well designed cell phones are required to transmit at widely varying power levels. However, a PA design that is highly efficient at a selected first power level is likely to be much less efficient at power levels that are either much higher or much lower than the selected first power level. Accordingly, PAs have been designed to use different physical circuitry depending upon which of two or more ranges the transmit power currently falls within. Such use of separate circuitry entails complex tradeoffs between features such as power efficiency integrated, circuit area, and performance.
It is clearly useful to increase the overall power and cost efficiency of such plural-range RF PAs. Inventive aspects of the power ranging RF PA described herein, used alone or in various combinations, will contribute to such overall power and/or cost efficiency of an RF PA embodying such aspects.